Has anyone else noticed a distinct lack of the usual birds?

There doesn't seem to be anything like the number there uses to be.

Also, one thing that stands out is the usual food that birds consume isn't getting eaten.

I noticed that Blackberries are just dropping off the briars (and later on, like last year many will just go to rot) and that applies to wild rasberries too.

There's a Damson tree on a bit of rough ground which is absoluely loaded, branches hanging under the weight of the crop and they're starting to split, they'll be dropping off soon. There's Elder bushes/trees weighed down with elderberries and the usual birds "purple slodges" are not apparent either.

There's all sorts of plants (weeds?) covered in seeds and no birds are taking them so what's going on?

It's been said about many species (not just birds) that the decline in numbers is put down to "loss of habitat" but that surely can't be the case with the birds? There's plenty of food so what gives?